Facet device and method

ABSTRACT

A spine implant includes an insert positioned between facets of a zygapophyseal joint. In various embodiments, the insert is configured to exert a distraction force on one or more facets of the zygapophyseal joint. The insert may comprise one or more members having one or more opposing facet interfacing portions. A securing member is configured to interface with the insert to secure the facets.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of Application No. 13/346,435,filed Jan. 9, 2012 and entitled “Facet Device and Method,” which is acontinuation of application Ser. No. 12/169,370, filed Jul. 8, 2008 andentitled “Facet Device and Method,” now U.S. Pat. No. 8,114,158, whichis a continuation-in-part of application Ser. No. 11/197,566, filed Aug.3, 2005 and entitled “Facet Device and Method,” now abandoned, whichclaims the benefit of U.S. Provisional Application No. 60/598,882, filedAug. 3, 2004 and entitled “Spine Treatment Devices and Methods,” all ofwhich are incorporated by reference herein in their entireties for allpurposes.

FIELD OF THE INVENTION

The invention relates to devices to treat the spine, in particular inassociation with a facet joint, including but not limited to spinalstabilization devices, spinal distraction devices, spinal prostheses,devices to treat pain associated with the spine, and other spinaltreatment devices.

DESCRIPTION OF THE RELATED ART

Certain spine conditions, defects, deformities (e.g., scoliosis) as wellas injuries may lead to structural instabilities, nerve or spinal corddamage, pain or other manifestations. Back pain (e.g., pain associatedwith the spinal column or mechanical back pain) may be caused bystructural defects, by injuries or over the course of time from theaging process. For example, back pain is frequently caused by repetitiveand/or high stress loads on or increased motion around certain boney orsoft tissue structures. The natural course of aging leads todegeneration of the disc, loss of disc height, and instability of thespine among other structural manifestations at or around the spine. Withdisc degeneration, the posterior elements of the spine bear increasedloads with disc height loss, and subsequently attempt to compensate withthe formation of osteophytes and thickening of various stabilizingspinal ligaments. The facet joints may develop pain due to arthriticchanges caused by increased loads. Furthermore, osteophytes in theneural foramina and thickening of spinal ligaments can lead to spinalstenosis, or impingement of nerve roots in the spinal canal or neuralforamina. Scoliosis also creates disproportionate loading on variouselements of the spine and may require correction, stabilization orfusion.

Pain caused by abnormal motion of the spine has long been treated byfixation of the motion segment. Spinal fusion is one way of stabilizingthe spine to reduce pain. In general, it is believed that anteriorinterbody or posterior fusion prevents movement between one or morejoints where pain is occurring from irritating motion. Fusion typicallyinvolves removal of the native disc, packing bone graft material intothe resulting intervertebral space, and anterior stabilization, e.g.,with intervertebral fusion cages or posterior stabilization, e.g.,supporting the spinal column with internal fixation devices such as rodsand screws. Internal fixation is typically an adjunct to attainintervertebral fusion. Many types of spine implants are available forperforming spinal fixation, including the Harrington hook and rod,pedicle screws and rods, interbody fusion cages, and sublaminar wires.

Alternatives have been proposed and tested to replace the need forspinal fusion to treat patients with back pain. These implants includeartificial discs and artificial nucleus technologies that preservemotion. However, these implants do not directly address the forces borneby the facet joints.

The facet joints provide a means for load transmission, support andmotion of the posterior spinal column. Disc height loss fromdegenerative disc disease and aging leads to increased load on the facetjoints, which can lead to arthritic, painful, degenerative changes.

Often over the course of degenerative disc disease there is a narrowingof the neural foramen through which the nerves exit the spine. Inaddition to the degeneration of discs causing the narrowing of theforamen, there is also calcification around the foramen causing furthernarrowing or stenosis resulting in pain to the patient. Currently, theseconditions may be treated by removing some or all of the lamina(laminectomy) or posterior bone adjacent or around the stenotic neuralforamen

Given that the facet joint and its environs is a source of pain for somepatients, some procedures have been developed or proposed to relievepain associated with the facet joint. Partial or complete removal of thepathological facets, and replacement with a mechanical joint thatpreserves motion similar to a facet has been proposed. Additionally,individual degenerative facet articulations have been replaced withcaps.

It would be desirable to provide improved devices and methods forrelieving pain associated with the facet joints.

Spinal stenosis pain or from impingement of nerve roots in the neuralforamina has been treated by laminectomy and foraminotomy, and sometimesreinforced with rod and screw fixation of the posterior spine.

More recently, as an alternative to laminectomies and relatedprocedures, implants have been proposed that distract the spine from aposterior approach. In particular, a wedge-like implant inserted betweentwo adjacent spinous processes has been proposed to relieve pressure onspinal nerves and nerve roots. A kyphosis is induced, which opens thespace of the spinal canal and neural foramen, thereby reducing theeffect of spinal stenosis. However, this type of distraction of adjacentspinous processes is suboptimal for several reasons: The resultingkyphosis is non-physiologic, leading to increased load on the anteriorportion of the disc and the vertebral bodies. This can increase the riskof disc degeneration and vertebral compression fracture. The implanttends to bend the spine forward. The spinous processes may fracture dueto the distraction forces of the wedge implant. Bone may collapse aroundthe spinous process. The implant may weaken, tear, or stretchstabilizing ligaments of the spine, such as the supraspinous ligament,interspinous ligament, ligamentum flavum, posterior longitudinalligament, or capsule of the zygapophyseal joint. The amount ofdistraction is not adjustable to the specific amount of stenosis, andcannot be easily readjusted months to years after the device has beenimplanted.

It would accordingly be desirable to provide a distraction device thatreduces or avoids some or all of these issues.

Pain due to instability of the spine has also been treated with dynamicstabilization of the posterior spine, using elastic bands that connectpedicles of adjacent vertebrae.

The typical techniques for fusion, decompression, and dynamicstabilization require open surgical procedures with removal ofstabilizing muscles from the spinal column, leading to pain, blood loss,and prolonged recovery periods after surgery due in part to thedisruption of associated body structures or tissue during theprocedures.

Accordingly, it would be desirable to provide less invasive devices andmethods for treating pain or discomfort associated with the spinalcolumn. It would also be desirable to provide such devices and methodsthat are less damaging to associated tissue.

Spine surgeons commonly use metallic or polymeric implants to effect oraugment the biomechanics of the spine. The implants frequently areattached or anchored to bone of the spine. Sites typically consideredappropriate for boney attachment have high density or surface area, suchas, for example, the pedicle bone, the vertebral body or the corticalbone of the lamina. The spinous process contains thin walls of corticalbone, and thus, has been considered as not ideal for anchoring spinalimplants as they may not support the implants under physiologic loads,or the intermittent high loads seen in traumatic situations. Fixationhas been attempted from spinous process to spinous process with poorresults.

A translaminar facet screw as used by some surgeons goes through thebase of spinous process to access the cancellous bone of the lamina. Adisadvantage of this device is that it is not suitable for attaching toa pedicle screw and the depth and angle during deployment can be verydifficult to track or visualize, thus increasing the possibility thatthe screw would extend into the spinal canal. A facet screw is screwedbetween opposing facets of a zygapophyseal joint.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to providing a deviceand method for alleviating discomfort and or deformity associated withthe spinal column. Another aspect of the present invention is directedto providing a minimally invasive implant and method for alleviatingdiscomfort associated with the spinal column. Another aspect of thepresent invention provides an anchoring device and method that requiresless surrounding tissue damage or disruption. Other aspects of theinvention may supplement or bear load for degenerated or painful joints,e.g., the facet joint.

One aspect of the invention provides for repair or reconstruction of adysfunctional facet joint. For example, by entering the capsule of thefacet joint, creating a space between articulating facets by removingsynovium, cartilage, and some bone from within the zygapophysial joint,and, then, inserting a motion preserving prosthesis. Motion preservingprostheses may include a smooth and/or curved surface, a sphere, an eggshaped/oval implant, or a self contained “ball and socket” joint.Magnetic plates with like poles facing each other may be attached tointerfacing articulating portions of the facets. Attachment of themotion preserving prosthesis may involve extensions from the prosthesisthat partially or completely penetrate each of the facets.

Another aspect of the invention provides for repairing the encapsulatingligaments with suture, adhesive, a patch, or other materials after acapsule of the zygapophysial joint has been invaded for tissue removaland insertion of a prosthesis. One aspect of the invention includes anelastic encapsulating wrap used to stabilize the facet joints.

According to an embodiment of the invention, a facet distraction implantis provided for maintaining a space that is formed between the facetarticulations of adjacent vertebrae when the joints are distracted. Thefacets may be distracted using a known distraction method or techniqueand an implant may be placed between the facets. A securing deviceaccording to the invention may be positioned to anchor each of the facetarticulations of a facet joint to each other in distraction to maintainthe opening of the corresponding neural foramen. The prosthesis mayinclude a distraction element that exerts a distracting force on thejoint.

Various aspects of the invention are set forth in the description and/orclaims herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a facet implant in accordance withthe invention.

FIG. 2 is a schematic side view of a facet implant in accordance withthe invention.

FIG. 3 is a schematic posterior lateral perspective view of a facetimplant in accordance with the invention.

FIG. 4 is a side partial cross section of a facet implant in accordancewith the invention.

FIG. 5 is a side partial cross section of a facet implant in accordancewith the invention.

FIG. 6 is a schematic posterior lateral perspective view of a stenoticneural foramen of a posterior spine.

FIG. 7 is a schematic posterior lateral view of a facet implant inaccordance with the invention.

FIG. 8 is a side schematic view of a facet implant in accordance withthe invention.

FIG. 9 is a side schematic view of a facet implant in accordance withthe invention.

FIG. 10 is a side schematic view of a facet implant in accordance withthe invention.

FIG. 11 is a side schematic view of a facet implant in accordance withthe invention.

FIG. 12 is a side schematic view of a facet implant in accordance withthe invention.

FIG. 13 is a side schematic view of a facet implant in accordance withthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-5 illustrate facet repair prostheses in accordance with anembodiment of the invention. Prosthesis 410 comprises a ball bearing 411implanted between the caudal and the cephalic facets 412, 413 of thezygapopyhseal joint. (FIG. 1) The joint is prepared by removing softtissue between the joints and creating a concavity on adjacent facetplates for receiving the ball bearing.

In FIG. 2, magnets 415, 416 including smooth interacting bearingsurfaces are respectively screwed into the cephalic and caudal facets417, 418 of the zygapopyhseal joint 419. The magnets 415, 416 areoriented so that like poles face each other (e.g. North-North orSouth-South) to provide a distraction force at the joint. The magnetsmay have a center hole through which a rod is inserted to resist thetendency of one magnet to move relative to the other. Each end of therod may have a diameter larger than the center holes. This system may beused in other joints in the body to maintain separation between thejoints.

Referring to FIG. 3, a joint prosthesis 420 is positioned between thecephalic and caudal facets 426, 427. The prosthesis comprises a ball 421providing a bearing surface for the motion of the facets 426, 427, andopposing posts 422, 423 screwed in or otherwise implanted in the facets426, 427, respectively for securing the ball 421 within the joint. Theball 421 may include openings for receiving the posts, e.g., in atapered interference type fitting, to secure the posts 422, 423 to theball 421 and to secure the ball 421 within the joint.

This facet repair may be performed percutaneously or via minimallyinvasive surgical techniques, for example using percutaneouslypositioned distracting instruments to distract the joint, for example,an expanding balloon or forceps like distractors. Using a hollow needlepercutaneously positioned into the joint, an expandable orself-expanding facet distraction implant may be placed in positionthrough the hollow lumen of the needle into the joint. A polymermaterial may be injected into the joint through a percutaneouslyinserted needle.

FIG. 4 illustrates a material 440 such as a polymer injected between thecephalic and caudal facets 426, 427. The material 440 forms a flexiblemember 441 that allows some movement of the joint due to the flexibleproperties and/or the shape that permit articulation of the joint. Asecuring member 442 extends through the facets 426, 427 and the material440 to further hold the member 441 in place in the joint capsule and/orto prevent implant extrusion. The securing member 442 includes anchors443, 444 that anchor to the outside or within the facets 426, 427 tohold the securing member 442 in place while permitting some motion forexample through spacing at or in the joint. The securing member 442 mayfor example, comprise a screw, or may be constructed of a flexiblematerial such as a flexible polymer. The securing member may alsocomprise a band constructed of fibers strands such as Kevlar™,polypropylene or polyethylene, or constructed of a fiber reinforcedpolymer. The anchors 443, 444 may be of a material such as titanium, orPEAK that may be screwed or crimped on to the securing member 442. Thepolymer may be injected into the joint capsule into opening 443 a in theanchor 443, through a lumen 442 a in the securing member 442 and throughholes 442 b or pores in the securing member 442. This may be done whenthe joint is distracted or otherwise positioned as desired.

FIG. 5 illustrates a material 450 such as a polymer injected between thecephalic and caudal facets 426, 427. The material 450 forms an implant451 that allows some movement of the joint due to the flexibleproperties and/or a shape that permits articulation of the joint. Asecuring member 452 extends through the facets 426, 427 and the material450 to further hold the implant 451 in place in the joint capsule. Thesecuring member 452 includes an anchor 453 that anchors the member tothe outside or within the facet 426, (or alternatively to the outside orwithin the facet 427) to hold the securing member 452 in place. Thesecuring member 452 further includes a tapered end that allows thesecuring member 452 to be inserted through the joint capsule andanchored into facet 427. The securing member may be a screw with athreaded tip 454 that screws into the bone. The securing member canfurther include a flexible portion that allows some movement of thesecuring member and joint. The anchor 453 may include an opening 453 ainto a lumen 452 a in the securing member 452, for injecting a polymerinto a lumen 452 a in the member and then through holes 452 b into thejoint capsule to form the implant 451.

According to the invention, a facet joint device as described herein maybe used in combination with an artificial disc or other spinal implants,e.g., to maintain the integrity of the facets. The facet jointdistraction or replacement devices and procedures described herein maybe used in conjunction with anteriorly placed implants, e.g., in a loadsharing arrangement. The facet joint resurfacing, distraction oraugmentation as well as the anterior implants may be used with a processto pedicle distraction or stabilizing device as described herein.Various spinal implants may also be used with facet resurfacing, facetdistraction or augmentation procedures.

In accordance with one aspect of the invention, narrowing or stenosis ofthe neural foramen may be treated using a device configured to distractthe facet joint. Accordingly, a distraction system is provided fordistracting the facet joint.

Referring to FIG. 6, a portion of the spine is illustrated withadjoining vertebrae prior to distraction. The neural foramen 250 betweena first vertebra 251 and a second vertebra 252 is stenotic. At thezygapophyseal joint capsule 253, there is no gap between the cephalicand caudal facets 254, 255.

Referring to FIG. 7, the portion of the spine of FIG. 6 is illustratedwith a facet distracter implant 256 in place between the cephalic facet254 and the caudal facet 255. The implant 256 comprises a distractingportion 257 and anchors 258, 259 comprising barbs or bone anchors. Thedistracting portion may include a distracting element as described withrespect to FIGS. 8-13 herein. The anchor 258 is positioned in bone abovethe cephalic facet 254 while the anchor 259 is positioned in the bonebelow the caudal facet 255. The facet distracter implant 256 includes asensor 256 a, the type of which may be selected to sense one of a numberof different parameters. Pressure sensors, strain gauges, or othersensors may be used to sense load seen by the facet joint. Thisinformation may be used to monitor the condition of the facet joint ordetermine if fusion may be necessary. The other facet joint implantsdescribed herein may also include similar sensors.

The procedure for implanting the device generally includes opening thezygapophyseal joint capsule with a scalpel. Then the adjacent vertebraeare distracted by one of a number of known distraction methods or bydistracting the joint mechanically using devices such as a wedge orexpanding rod or balloon between adjacent spinous processes, or betweenother parts of adjacent vertebrae. The tissue between the facets 254,255 is then debrided and/or denervated. The implant is then insertedbetween the facets 254, 255 after the joint is distracted. The anchors258, 259 engage the interfacing portions of the bone of the facets 254,255.

FIG. 8 illustrates a distracter implant 260 positioned between facets254, 255. The distracter implant 260 comprises a block 261 wedgedbetween the facets 254, 255. In FIG. 9 an alternative distracter 262implant comprises a ball 263. In FIG. 10 an active distracter implant265 comprise a coiled spring 266. In FIG. 11, the distracter implant 265a comprises an expandable polymer 266 a, e.g., a hydrogel or expandablegel foam. In FIG. 12 the distracter implant 267 comprise an expandablemember 268 that may be expanded to distract the joint 253 by inflatingwith a curable polymer, a liquid, gas or other material. The distractionmay occur after implantation to adjust the level of distraction. Theexpandable member may also be adjusted after implanting by increasing orremoving the inflation medium, e.g. using a needle or accessing themember through a one-way valve. FIG. 13 illustrates a shrink-wrap 269placed partially around the joint 253. The shrink-wrap or other materialcomprises, e.g., a Dacron material that holds the block 261 or otherimplant in place between facets 254, 255. The material may encourageingrowth of tissue. The material may be coated with a material thatreduces tissue ingrowth to permit the joint to move or reduces adhesionsto prevent pain. The material may include burrs or barbs that secure thematerial to the bone or it may be secured, e.g. with suture anchors. Theimplants may be constructed, for example, of a metal, polymer orceramic, may be coated or imbedded with therapeutic agents (e.g. asteroid or lidocaine) or other material.

What is claimed is:
 1. A facet implant comprising: an insertpositionable between a first facet of a facet joint and a second facetof the facet joint, the insert configured to exert a distraction forceon the first and second facets; an anchor connected to the insert andconfigured to secure to one of the first and second facets; and a sensorcoupled to the insert and configured to sense load on the facet joint.2. The facet implant of claim 1, wherein the anchor includes a boneanchor.
 3. The facet implant of claim 1, wherein the anchor includes abarb.
 4. The facet implant of claim 1, further including a second anchorconnected to the insert and configured to secure to the other of thefirst and second facets.
 5. The facet implant of claim 1, wherein theinsert includes a block configured to wedge between the first and secondfacets.
 6. The facet implant of claim 1, wherein the insert includes aball.
 7. The facet implant of claim 1, wherein the insert includes acoiled spring.
 8. The facet implant of claim 1, wherein the insertincludes an expandable polymer.
 9. The facet implant of claim 8, whereinthe expandable polymer includes a hydrogel, a gel foam, or combinationsthereof.
 10. The facet implant of claim 1, wherein the insert isconfigured to inflate and distract the facet joint when the insertreceives an inflation medium therein while positioned within a facetjoint capsule defined between the first and second facets, the inflationmedium including a curable polymer, a liquid, a gas, or combinationsthereof.
 11. The facet implant of claim 10, wherein the inflation mediumis selectively removable from the insert to adjust dimensions of theinsert.
 12. The facet implant of claim 1, further including ashrink-wrap material secured at least partially around the insert. 13.The facet implant of claim 12, wherein the shrink-wrap material includesa polymeric material.
 14. The facet implant of claim 12, wherein theshrink-wrap material includes a coating adapted to reduce tissueingrowth.
 15. The facet implant of claim 12, wherein the shrink-wrapmaterial includes burrs or barbs.
 16. The facet implant of claim 1,wherein the insert is formed of metal, polymer, ceramic, or combinationsthereof.
 17. The facet implant of claim 1, wherein the insert includes atherapeutic agent.
 18. A method for repairing a facet joint, the methodcomprising: positioning an insert between a first facet of a facet jointand a second facet of the facet joint to maintain separation between thefirst and second facets; anchoring the insert within a joint capsuledefined between the first and second facets of the facet joint; andmonitoring changes in condition of the facet joint with a sensoroperatively coupled to the insert.
 19. The method of claim 18, furtherincluding distracting the facet joint to enable the insert to bepositioned within the joint capsule.
 20. The method of claim 19, furtherincluding at least one of debriding and denervating tissue disposedbetween the first and second facet joints to facilitate positioning ofthe insert within the joint capsule.